I have some design questions about a pergola design. It will be 14 feet wide by 12 feet long and made from pressure treated lumber (painted). I am replacing a pergola attached to my townhouse on two sides. The two sides of the townhouse form an “L” shape. I want to cover the pergola with polycarbonate sheets.
Because of my community regulations, I can’t expose the cover. So, my idea is to space my 2 x 10 rafters 24 inches apart and then attach 2 x 2’s inside the rafters creating a 4:12 slope. The polycarbonate would be fastened to the 2 x 2’s and supported with a 2 x 2 cross member every 2 feet. I live in Miami Florida and plan to use hail proof polycarbonate.
Similar to the method used to attach the polycarbonate sheeting, I would run another 2 x 2 inside the rafters creating 2’ x 2’ boxes that will have bamboo matting stapled to it. Lastly, to create a finished look, I would cover the visible perimeter of the boxes after the bamboo is stapled with 1 x 2’s.
My 14-foot wide beam will be 3 2 x 10’s sandwiched together with adhesive and screws and then attached to the top of my 6 x 6 post with BCS post caps. The 2 x 10’s would have to span 10 feet from the side of the house to the top cross member. The 2 x 10’s would be fastened to the house using joist hangers. They would not be visible from below.
Is my design idea faulty, will the 3 2 x 10’s support the load of the pergola? Will the 10' span of the rafters be okay with the minimal added weight of the polycarbonate and bamboo? Do I have enough slope to allow for drainage of rain water? Any ideas are welcome. Thanks
You really need to prepare plans and show them to your local building inspector. Or talk to the building inspector first, then prepare plans based on local code.
Personally I have no idea what code requirements are for pergolas with polycarbonate roofing in Florida, but I am quite certain your building inspector will be able to help you there. I am not trying to blow you off, but asking for free design help over the internet on a project specific issue is not likely to get you far. At worst, you could get "assistance" that is not code compliant in your area, which would potentially be a mess if you followed it.